package org.andengine.util.algorithm.collision;

import org.andengine.opengl.util.VertexUtils;
import org.andengine.util.Constants;


/**
 * (c) 2010 Nicolas Gramlich
 * (c) 2011 Zynga Inc.
 *
 * @author Nicolas Gramlich
 * @since 11:50:19 - 11.03.2010
 */
public class ShapeCollisionChecker extends BaseCollisionChecker {
    // ===========================================================
    // Constants
    // ===========================================================

    // ===========================================================
    // Fields
    // ===========================================================

    // ===========================================================
    // Constructors
    // ===========================================================

    // ===========================================================
    // Getter & Setter
    // ===========================================================

    // ===========================================================
    // Methods for/from SuperClass/Interfaces
    // ===========================================================

    // ===========================================================
    // Methods
    // ===========================================================

    /**
     * Calls through to {@link ShapeCollisionChecker#checkCollisionSub(float[], int, int, int, int, int, float[], int, int, int, int)} with the default parameters internally used by different AndEngine primitives.
     *
     * @param pVerticesA
     * @param pVertexCountA the number of vertices in pVerticesA
     * @param pVerticesB
     * @param pVertexCountB the number of vertices in pVerticesB
     * @return
     */
    public static boolean checkCollision(final float[] pVerticesA, final int pVertexCountA, final float[] pVerticesB, final int pVertexCountB) {
        return ShapeCollisionChecker.checkCollision(pVerticesA, pVertexCountA, Constants.VERTEX_INDEX_X, Constants.VERTEX_INDEX_Y, 2, pVerticesB, pVertexCountB, Constants.VERTEX_INDEX_X, Constants.VERTEX_INDEX_Y, 2);
    }

    /**
     * @param pVerticesA
     * @param pVertexCountA   the number of vertices in pVerticesA
     * @param pVertexOffsetXA
     * @param pVertexOffsetYA
     * @param pVertexStrideA
     * @param pVerticesB
     * @param pVertexCountB   the number of vertices in pVerticesB
     * @param pVertexOffsetXB
     * @param pVertexOffsetYB
     * @param pVertexStrideB
     * @return
     */
    public static boolean checkCollision(final float[] pVerticesA, final int pVertexCountA, final int pVertexOffsetXA, final int pVertexOffsetYA, final int pVertexStrideA, final float[] pVerticesB, final int pVertexCountB, final int pVertexOffsetXB, final int pVertexOffsetYB, final int pVertexStrideB) {
        /* Check all the lines of A ... */
        for (int a = pVertexCountA - 2; a >= 0; a--) {
            /* ... against all lines in B. */
            if (ShapeCollisionChecker.checkCollisionSub(pVerticesA, pVertexOffsetXA, pVertexOffsetYA, pVertexStrideA, a, a + 1, pVerticesB, pVertexCountB, pVertexOffsetXB, pVertexOffsetYB, pVertexStrideB)) {
                return true;
            }
        }
        /* Also check the 'around the corner of the array' line of A against all lines in B. */
        if (ShapeCollisionChecker.checkCollisionSub(pVerticesA, pVertexOffsetXA, pVertexOffsetYA, pVertexStrideA, pVertexCountA - 1, 0, pVerticesB, pVertexCountB, pVertexOffsetXB, pVertexOffsetYB, pVertexStrideB)) {
            return true;
        } else {
			/* At last check if one polygon 'contains' the other one by checking
			 * if one vertex of the one vertices is contained by all of the other vertices. */
            if (ShapeCollisionChecker.checkContains(pVerticesA, pVertexCountA, VertexUtils.getVertex(pVerticesB, pVertexOffsetXB, pVertexStrideB, 0), VertexUtils.getVertex(pVerticesB, pVertexOffsetYB, pVertexStrideB, 0))) {
                return true;
            } else if (ShapeCollisionChecker.checkContains(pVerticesB, pVertexCountB, VertexUtils.getVertex(pVerticesA, pVertexOffsetXA, pVertexStrideA, 0), VertexUtils.getVertex(pVerticesA, pVertexOffsetYA, pVertexStrideA, 0))) {
                return true;
            } else {
                return false;
            }
        }
    }

    /**
     * Checks line specified by <code>pVertexIndexA1</code> and <code>pVertexIndexA2</code> in <code>pVerticesA</code> against all lines in <code>pVerticesB</code>.
     *
     * @param pVerticesA
     * @param pVertexOffsetXA
     * @param pVertexOffsetYA
     * @param pVertexStrideA
     * @param pVertexIndexA1  the first point of the line in pVerticesA
     * @param pVertexIndexA2  the second point of the line in pVerticesA
     * @param pVerticesB
     * @param pVertexCountB   the number of vertices in pVerticesB
     * @param pVertexOffsetXB
     * @param pVertexOffsetYB
     * @param pVertexStrideB
     * @return
     */
    private static boolean checkCollisionSub(final float[] pVerticesA, final int pVertexOffsetXA, final int pVertexOffsetYA, final int pVertexStrideA, final int pVertexIndexA1, final int pVertexIndexA2, final float[] pVerticesB, final int pVertexCountB, final int pVertexOffsetXB, final int pVertexOffsetYB, final int pVertexStrideB) {
		/* Check against all the lines of B. */
        final float vertexA1X = VertexUtils.getVertex(pVerticesA, pVertexOffsetXA, pVertexStrideA, pVertexIndexA1);
        final float vertexA1Y = VertexUtils.getVertex(pVerticesA, pVertexOffsetYA, pVertexStrideA, pVertexIndexA1);
        final float vertexA2X = VertexUtils.getVertex(pVerticesA, pVertexOffsetXA, pVertexStrideA, pVertexIndexA2);
        final float vertexA2Y = VertexUtils.getVertex(pVerticesA, pVertexOffsetYA, pVertexStrideA, pVertexIndexA2);

        for (int b = pVertexCountB - 2; b >= 0; b--) {
            final float vertexB1X = VertexUtils.getVertex(pVerticesB, pVertexOffsetXB, pVertexStrideB, b);
            final float vertexB1Y = VertexUtils.getVertex(pVerticesB, pVertexOffsetYB, pVertexStrideB, b);
            final float vertexB2X = VertexUtils.getVertex(pVerticesB, pVertexOffsetXB, pVertexStrideB, b + 1);
            final float vertexB2Y = VertexUtils.getVertex(pVerticesB, pVertexOffsetYB, pVertexStrideB, b + 1);
            if (LineCollisionChecker.checkLineCollision(vertexA1X, vertexA1Y, vertexA2X, vertexA2Y, vertexB1X, vertexB1Y, vertexB2X, vertexB2Y)) {
                return true;
            }
        }
		/* Also check the 'around the corner of the array' line of B. */
        final float vertexB1X = VertexUtils.getVertex(pVerticesB, pVertexOffsetXB, pVertexStrideB, pVertexCountB - 1);
        final float vertexB1Y = VertexUtils.getVertex(pVerticesB, pVertexOffsetYB, pVertexStrideB, pVertexCountB - 1);
        final float vertexB2X = VertexUtils.getVertex(pVerticesB, pVertexOffsetXB, pVertexStrideB, 0);
        final float vertexB2Y = VertexUtils.getVertex(pVerticesB, pVertexOffsetYB, pVertexStrideB, 0);
        if (LineCollisionChecker.checkLineCollision(vertexA1X, vertexA1Y, vertexA2X, vertexA2Y, vertexB1X, vertexB1Y, vertexB2X, vertexB2Y)) {
            return true;
        }
        return false;
    }

    /**
     * Calls through to {@link ShapeCollisionChecker#checkContains(float[], int, int, int, int, float, float)} with the default parameters internally used by different AndEngine primitives.
     *
     * @param pVertices
     * @param pVertexCount the number of vertices in pVertices
     * @param pX
     * @param pY
     * @return
     */
    public static boolean checkContains(final float[] pVertices, final int pVertexCount, final float pX, final float pY) {
        return ShapeCollisionChecker.checkContains(pVertices, pVertexCount, Constants.VERTEX_INDEX_X, Constants.VERTEX_INDEX_Y, 2, pX, pY);
    }

    /**
     * Works with complex polygons!
     *
     * @param pVertices
     * @param pVertexCount   the number of vertices in pVertices
     * @param pVertexOffsetX
     * @param pVertexOffsetY
     * @param pVertexStride
     * @param pX
     * @param pY
     * @return <code>true</code> when the point defined by <code>(pX, pY)</code> is inside the polygon defined by <code>pVertices</code>, <code>false</code>. If the point is exactly on the edge of the polygon, the result can be <code>true</code> or <code>false</code>.
     * @see http://alienryderflex.com/polygon/
     */
    public static boolean checkContains(final float[] pVertices, final int pVertexCount, final int pVertexOffsetX, final int pVertexOffsetY, final int pVertexStride, final float pX, final float pY) {
        boolean odd = false;

        int j = pVertexCount - 1;
        for (int i = 0; i < pVertexCount; i++) {
            final float vertexXI = VertexUtils.getVertex(pVertices, pVertexOffsetX, pVertexStride, i);
            final float vertexYI = VertexUtils.getVertex(pVertices, pVertexOffsetY, pVertexStride, i);
            final float vertexXJ = VertexUtils.getVertex(pVertices, pVertexOffsetX, pVertexStride, j);
            final float vertexYJ = VertexUtils.getVertex(pVertices, pVertexOffsetY, pVertexStride, j);

            if ((((vertexYI < pY) && (vertexYJ >= pY)) || ((vertexYJ < pY) && (vertexYI >= pY))) && ((vertexXI <= pX) || (vertexXJ <= pX))) {
                odd ^= ((vertexXI + (((pY - vertexYI) / (vertexYJ - vertexYI)) * (vertexXJ - vertexXI))) < pX);
            }
            j = i;
        }

        return odd;
    }

    // ===========================================================
    // Inner and Anonymous Classes
    // ===========================================================
}
